The oral cavity contains many different species of bacteria. Some species of oral pathogenic bacteria (e.g. Porphyromonas gingivalis, Tannerella forsythia and Aggregatibacter actinomycetemcomitans) have been implicated in the development of periodontal diseases, such as periodontitis, gingivitis, necrotizing periodontitis, necrotizing gingivitis and peri-implantitis. Certain species of oral pathogenic bacteria have been implicated in tooth decay (e.g. Streptococcus mutans).
It is believed that certain species of oral bacteria are beneficial for maintaining the health of the periodontium. Without being bound by any theory, it is believed that these beneficial oral bacteria can interfere with colonization by pathogenic oral bacteria of the oral epithelium. For example, studies have shown that Streptococcus sanguinis, Streptococcus mitis and Streptococcus salivarius have inhibitory effects on A. actinomycetemcomitans colonization of epithelial cells in vitro (W. Teughels et al., J Dent Res 86(7), 611-617, 2007). It has also been shown, using a canine model, that the application of beneficial bacteria to periodontal pockets following root planing delays and reduces recolonization of the periodontal pockets by pathogenic bacteria (W. Teughels, et al., J Dent Res, 86(11), 1078-1082, 2007). The beneficial bacteria Streptococcus sanguinis, Streptococcus mitis and Streptococcus salivarius have also been shown to inhibit A. actinomycetemcomitans-induced production of the inflammatory cytokine interleukin-8 (IL-8) by the human oral keratinocyte cell line HOK-18A, which inflammatory response is implicated in periodontitis-related tissue destruction (I. Sliepen et al., J Dent Res 88(11), 1026-1030, 2009).
It is believed that selective stimulation of beneficial oral bacteria may provide a valid preventative approach for oral health, for example in the prevention of periodontitis.